迭代字典时出现“NoneType”对象不可迭代错误

Question

这是一个函数类：

def play_best_hand(hand, wordDict):

tempHand = hand.copy()
points = 0
for word in wordDict:
    for letter in word:
        if letter in hand:
            tempHand[letter] = tempHand[letter] - 1 
            if tempHand[letter] < 0:
                return False
            if wordDict[word] > points:
                bestWord == word
                points = wordDict[word]
return bestWord

这是我的错误追踪信息。第209行对应的是'for word in wordDict'这一行。

 Traceback (most recent call last):
    File "ps6.py", line 323, in <module>
    play_game(word_list)
  File "ps6.py", line 307, in play_game
    play_hand(hand.copy(), word_list)
  File "ps6.py", line 257, in play_hand
    guess = play_best_hand(hand, wordDict)
  File "ps6.py", line 209, in play_best_hand
    for word in wordDict:
TypeError: 'NoneType' object is not iterable

Answer 1

在 play_best_hand() 这个函数里，你写了：

if wordDict[word] > points:
    bestWord == word

你可能是想要进行赋值，而不是在比较是否相等：

if wordDict[word] > points:
    bestWord = word

Answer 2

这句话的意思是，变量 wordDict 现在是 None，而不是一个字典。这说明在调用 play_best_hand 的函数里出现了错误。可能是你在某个函数里忘记了 return 一个值，所以它返回了 None？